According to the electronic display on the ship’s bridge, the Galatea was suddenly flying at Mach speeds over northern Europe and Ireland. When Last activated the jammer, the ship went haywire. So he used a simple jamming device that overwhelmed the GPS signal by broadcasting noise on the same frequency as the satellites. Last wanted to find out how it would cope without GPS. The Galatea is the pride of its fleet, with all the latest navigation equipment. In 2010, he conducted an experiment in the North Sea, aboard the THV Galatea, a 500-tonne ship. Last has first-hand experience of how easy it is to block a GPS signal, and the effects it can have on modern technology. You can’t boost the signal any further because of the limited power supply on a satellite. It’s like a car headlight 20,000 kilometres away,” says consultant David Last, former president of the UK’s Royal Institute of Navigation. “The problem is that the GPS signal is very weak. Nowadays, many receivers also use GPS for cheap and convenient access to the accurate time given by the satellites’ clocks. Once it locks on to at least four satellites and has accounted for errors, it will discover its precise location (see graphic). A GPS receiver compares the time with its own clock, and then calculates how far it must be from each satellite. The dominant provider is still the US military’s NavStar network, with at least 24 satellites operating at any given time, positioned so that you can always see four of them from anywhere on the planet’s surface.Įach satellite continually broadcasts its location and the time as measured by its on-board atomic clock. GPS works thanks to radio signals from satellites. No surprise, then, that researchers across the world are scrambling to find ways to prevent disastrous GPS outages happening. One jammer can take out GPS from several kilometres away, if unobstructed. Their increasing use has already caused problems at airports and blocked cellphone coverage in several cities.
These can be bought on the internet, and tend to be used by say, truckers who don’t want their bosses to know where they are. Their biggest concern is a GPS jammer – a plastic device that can sit on car dashboards. Some are worried that we are now leaning too heavily on a technology that can all too easily fail – and it doesn’t need a freak navy training exercise to cause havoc. Unwittingly, they also blocked radio signals from GPS satellites across a swathe of the city.
To test procedures when communications were lost, technicians jammed radio signals. Two navy ships in the San Diego harbour had been conducting a training exercise. It took three days to find an explanation for this mysterious event in January 2007. On the streets, people reaching for their cellphones found they had no signal and bank customers trying to withdraw cash from local ATMs were refused. Chaos threatened in the busy harbour, too, after the traffic-management system used for guiding boats failed. At the Naval Medical Center, emergency pagers used for summoning doctors stopped working. In the tower at the airport, air-traffic controllers peered at their monitors only to find that their system for tracking incoming planes was malfunctioning. IT WAS just after midday in San Diego, California, when the disruption started.
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